High performance seaplane or amphibian

ABSTRACT

A high performance, low drag, high density seaplane having low reserve buoyancy and a low wing with a central hull supporting passenger cockpit unit thereabove, said hull carrying a hydrofoil beneath for quick takeoff, the central hull also acting as a main fuselage supporting the tail assembly. The power plant may be located in the cockpit unit or in the tail unit.

United States Patent Eugene H. Handler 4217 Brookfieid Drive,Kensington, Md. 20795 839,466

July 7, 1969 Aug. 17, 1971 [72] inventor [21 1 Appl. No. [22] Filed [45]Patented [54] HIGH PERFORMANCE SEAPLANE OR AMPHIBIAN 4 Claims, 4 DrawingFigs.

[52] U.S.C1 2'44/13, 244/101, 244/105 [5 l Int. Cl. 1364c 35/00 [50]Field olSearch 244/13,

[56] Reierences Cited UNITED STATES PATENTS 1,825,578 9/1931 Cemuda244/35 2,793,827 5/1957 Ries et a1. 244/105 D126,523 8/1940 Eaton, Jr.244/105 1,400,262 12/ 1921 Caproni 244/ 105 3,207,246 9/1965 Weiland244/23 3,498,247 3/1970 Handler 114/665 H Prim ary Examiner-MiltonBuchler Assistant Examiner-Steven W. Weinrieb AttorneysL. A. Miller, Q.E. Hodges and A. Sopp ABSTRACT: A high performance, low drag, highdensity seaplane hailing low reserve'buoyancy and a low wing with acentral hull supporting passenger cockpit unit thereabove, said hullcarrying a hydrofoil beneath for quick takeoff, the central hull alsoacting as a main fuselage supporting the tail assembly. The power plantmay be located in the cockpit unit or in the tail unit.

STATIC PATENTED AUG] 7 lHII SHEET 1 [IF 2 INVENTOR EuaEA/E H. HANDLER Wae My E

ATTORNEYS PATENTEUmsmsn I $599,903

SHEET 2 [IF E 6 INVENTOR U ENE H. HANDLER FIG. 4.

ATTORNEYS men PERFORMANCE SEAPLANE R AMIPHIBIAN BACKGROUND OF THEINVENTION A conventional flying boat (seaplane carrying the crew in thehull) has enormous reserve buoyancy (volume) to keep the crew, wing andengines clear of water and spray under all expected operatingconditions. This large volume results in large frontal and lateral area,which causes high aerodynamic drag. The structure of a large volumeflying boat hull weighs more than the much smaller fuselage of acorresponding land plane. In general it may be said that large volume ofan airplane is generally equivalent to low density, and low densityimplies low speed. I

If a seaplane is to achieve high aerodynamic performance, it must haveminimum volume, frontal and lateral area, as in the case of a fighteraircraft and high speed bomber or jet transport. The purpose of thisinvention is to provide a water-based aircraft performance comparable toa high performance land plane, and this can be achieved only by adrastic reduction in aerodynamic drag (frontal and surface area) andconsequently hull volume. Therefore, the crew must be moved from thehullto a nacelle clear of the water. This, of course, is true of anyconventional land plane mounted on twin floats, but in this case thereexists a redundancy of volume: the floats and the fuselage. Thisconversion also adds, in general, a startling array of struts, spreaderbars, guy wires, and other dragproducing items.

SUMMARY OF THE INVENTION This invention provides a low drag high densityseaplane of unique design, making use of a hydroski or supercavitatinghydrofoil as part of the hydrodynamic system. The wing is placed verynear, but above, the static waterline, thereby eliminating struts to thewing floats, and substantially increasing aerodynamic lift due to groundeffect. This location also places the wing in the spray pattern, butthis slight penalty is considered acceptable during the low speed phaseof takeoff. Reserve buoyancy of the hull is about 25 percent and may beless rather than the traditional 200 percent400 percent. Length/beamratio is about to (the hull may resemble the general series of highlength/beam ratio hulls developed by NACA) or alternatively may be astreamlined body of revolution with longitudinal steps or strips. Thirtyto 40 percent deadrise or a rounded bottom may be provided to give goodload alleviation and spray deflection during takeoffs and landings. Ashallow step just forward of the CG. may be employed. The step may beretractable.

The pilot and engine are carried in a streamlined nacelle supported by afaired strut to produce minimum drag. Propellers may be tractor, pusher,or both. Jet propulsion may also be employed provided that the intake islocated in a spray free location. The tail structure mounted on the hullshould have the surfaces located clear of main spray and thus a tee tailis employed since it may also be located in the propeller slipstream. Abutterfly tail may be used as an alternative. An alternative embodimenthas the engine mounted at the intersection of the vertical andhorizontal tails with the pilot nacelle moved forward to preserve theC.G. location.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1, 2 and 3 are respective plan,side and front views of one embodiment of an aircraft constructed inaccordance with the present invention, and

FIG. 4 is a side view of another embodiment of an aircraft constructedaccording to the present invention.

DETAILED DESCRIPTION AND OPERATION OF THE INVENTION Referring to thedrawings in which like reference numerals indicate like parts, and toFIGS. 13 in particular, the seaplane or craft of the present inventionis designated generally by numeral 11. Seaplane 11 has a centrallongitudinal hull 13 of slim, faired form with a length-to-beam ratio ofthe order of about 15 or more and a stepped hydroplane underbodycomposed of a Vee bottom section 15 and a step 17. The reserve buoyancyof the hull 13 when loaded is about 25 percent as generally indicated bythe location of the static waterline W.L.

The hull 13 is the principal longitudinal structural member of the craftand in addition houses control lines for the tail section. The hullcarries thereabove body means including a cockpit/engine unit 19 andtail unit 21. The cockpit/engine unit 19 may carry any suitable powerplant and as shown is supported above the CG. and near the midsection ofthe hull 13 by an upstanding faired strut 23 of sufficient height so asto provide clearance above the hull for jet intake or, as illustrated,for blades of a tractor propeller 25 mounted forwardly on the unit 19.The tail unit 21 is mounted at the aft end of hull 13 and has anessentially upstanding tail rudder section 27 near the top of which islocated on elevator unit 29 well above the static waterline W.L.

The seaplane has a low monowing 31 and as best seen in FIGS. 2 and 3 iscentrally supported from about the midpoint of faired strut 23. The wing31 as shown has a swept back leading edge and terminates at each of itsextremities at a downstanding strut 33, which constitutes along with tipfloats an aerodynamic end plate for the wing. The strut 33 at each wingtip supports a hydroplaning tip float 35 of slim, faired shape. Theunderbody of each tip float has a Vee bottom and may be provided with astep, if desired, said floats having suitable reserve buoyancy andsufficient immersion to laterally stabilize the craft.

The wing 31 is mounted sufficiently close to the static waterline W.L.as to provide substantial ground effect for the aircraft therebyincreasing its low speed lift. The wing 31 may be provided withwatertight means, such as enclosed spaces to render additional buoyancyto the craft. While the wing 31 is shown mounted to extend from thestrut 23, it is to be understood that the wing may alternatively bemounted to extend from the hull 13, or from atop the hull 13, with onlya very small clearance above the static waterline. As illustrated, theclearance of said wing above the static waterline may be preferably lessthan a quarter of the wing chord.

In order to further enhance the hydrodynamic characteristics of thecraft, a supercavitating hydrofoil or hydroski 37 is mounted on anelongated strut depending beneath the hull 13 slightly forward of thecenter of gravity so as to provide a nose up attitude of the craftduring landing and takeoff. The hydroski or hydrofoil 37 provides thefollowing characteristics for the craft while the foil or ski is stillcompletely submerged at low speeds:

1. It damps heave and pitch motions of the craft.

2. It unloads the hull, reducing wave-induced heave and pitch forces.

3. The hull-generated spray is decreased because of the reducedhydrodynamic loads on the hull. Resistance due to spray is lessened.

4. Hull resistance is substantially reduced, sine: esistance is roughlyproportional to hull loading.

5. Time from start of run to hull-planing phase is shortened.

Once the total weight of the craft is carried by the ski or fcil plusthe wing, the hull is completely clear of the water surface, resultingin the following characteristics:

1. Pitch and heave motions become negligible as foil or ski cuts throughwaves.

2. Hull generated spray and related resistance decreases to zero.

3. Only light spray and low resistance is generated by the ski or foil.

4. The seaplane responds rapidly to aerodynamic control.

5. The seaplane rapidly accelerates to takeoff 6. Rough watercapabilities are enormously improved.

In accordance with the teaching of this invention, it is seen that sincethe foil or ski unloads the hull, reduces wave impacts, loads due tospray, etc., the aircraft structure can be appropriately lightened.Spray strips can be reduced, the step depth can be decreased, and thehull can be more readily designed to aerodynamic rather thanhydrodynamic considerations. The height of components, dictated by sprayconsiderations, can be reduced.

The strut-supported hydroski or hydrofoil 37 may be mounted permanentlyor retractably in any suitable well known manner so that its rathersmall amount of drag can be partiallyor totally eliminated when thecraft is completely airborne.

As illustrated in FIG. 1, the seaplane 11 may be provided withretractable landing gear such as bicycle gear composed of retractablewheels 39, 41 tandemly disposed along the centerline of the hull 13 andretractable wheels 43, 45 in the tip floats 35. Other landing gearconfigurations may, of course, be employed, such as tricycle gear with abow wheel in the nose of the hull with the main wheels retractable inthe wings, or a tail wheel system with main gear retracting into thewings or hull.

Reference is now made to FIG. 4 illustrating a seaplane or craft 41arranged in accordance with another embodiment of the invention. Thecraft 41 has a central longitudinal planing hull 43 of slim proportionsas described in connection with FIGS. 1-3, a low monowing 45, tip floats47 supported by depending struts 49 at the wing extremities, and ahydroski or supercavitating hydrofoil 51 located on a depending strutjust forward of and beneath the C6. of the craft. The craft has acockpit unit 53 mounted in an upstanding strut 55 located well forwardof the CG. and unlike the embodiment of FIGS. 1- 3, does not include thepower plant.

A tail unit 57 is mounted on the'aft end of the hull 13 and has a ruddersection 59 and an elevator section 61 locate well above the staticwaterline W.I... Extending forwardly from elevator'sec tion 61 is anacelle 63 carrying a power plant which may be of any suitable designsuch as jet, rocket, turbo fan, turbo prop, etc., and here illustratedas a tractor propeller 65.

The craft shown in the FIG. 4 embodiment performs in es sentially thesame manner as that of FIGS. 1+3, and has the advantage of locating thepropeller more remotely from the cockpit and from the sprayarea.

DESCRIPTION OF OPERATION As previously indicated, the seaplane hullwhile at rest has about 25 percent reserve buoyancy. The wing 31, if theseaplane is light and small, may be only a few inches or about a footabove the static waterline, and the ski or foil below static waterlineabout 1 to 3 feet. During takeoff, with the hydroski or supercavitatinghydrofoil extended, the ski or foil and hydroplane hull and tip floatsurfaces lifts the aircraft and provides at low speeds the earlyattainment of low hydrodynamic drag. The wing 31 provides ground effectand airfoil lift so that, as the hydroplaning surfaces begin to clearthe water surface, the hydroski or hydrofoil itself provides allhydrodynamic lift. Thus, wetted hydroplaning surfaces with attendantsuction characteristics are avoided as the craft approaches aerodynamictakeoff speed, thereby enabling less drag and quicker attainment oftakeoff speed. As the craft, including the ski or foil, completely liftsoff and the craft becomes airborne, the ski or foil may be completelyretracted in any suitable well known manner, or less than completelyretracted, as by being pulled up into hull 13 or 41 until the leadingedge is flush with the under surface of said hull. In this position thedrag penalty of the ski is only slight. During landing, the ski or foilis extended and is first to contact the water surface, thereby providinglow hydrodynamic drag and thus a gentle transition of the craft fromairborne to waterborne speed.

In carrying out the present invention it is appreciated that where thewings are negatively dihedral the struts 33 may be eliminated, said wingtips terminable directly at tip floats.

Further, because the wing of the present invention is sufficiently closeto the water to enable substantial ground effect lift, cumbersome flapswith attendant corrosive equipment such as hinges, rods, etc., mayadvantageously be eliminated. Further, if desired, spoilers may beemployed for control purposes instead of ailerons as generallyindicated. Of course, the number and disposition of hydrofoils orhydroskis may be varied from the arrangement illustratively shown. Forexample, hydrodynamic lifting means may comprise a hydrofoil or skielement located at the bottom of a strut depending from each wing. Also,plural hydrofoil elements may be employed on each depending strut, andas a substitute for the single foil or ski 37 exemplarily shown in thedrawings.

It is further understood that while employment of a hydroski orhydrofoil element is advantageous to the working of the invention, theseaplane arrangement will nevertheless operate with some loss ofefficiency without said element. In such a case the takeoff angle willbe reduced depending upon orientation of the wings, thrust, and presenceand extent of a hydroplane step.

It is to be understood that while the sizes of the seaplanes depictedillustratively in the drawings are small, the principles of the presentinvention apply also to larger craft, the size of the craft not beingcritical to the invention.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that the invention may be practiced otherwise than asspecifically described.

What I claim is:

l. A low drag, high density seaplane having performance characteristicslike that of a high speed land plane of approximately the same size,comprising:

a central longitudinal aerodynamically designed hull of approximately 25percent reserve buoyancy and having a high length to beam ratio ofapproximately 15:1;

a first faired strut means connected at one end thereof to said hull andextending upwardly from said hull;

a flapless monowing centrally supported at the other end of said firstfaired strut means, said monowing being located a maximum of one-fourthof the wing chord above the static waterline of said hull therebycreating a ground effect with respect to the water, said monowing havinga spoiler mounted on the upper surface thereof;

tip float means connected to the extreme ends of said monowing whichprovide lateral, hydrodynamic stability, the proximity of said tip floatmeans to said monowing prevents excessive loss through wing tipvortices;

a second faired strut means connected at one end thereof and extendingupwardly from said monowing;

an aerodynamically configured body means including a personnel carryingsection supported at the other end of said second faired strut means;

tail means removed from said body means connected to said hull at therear end thereof; and

a hydrodynamic lifting means connected to d hull for producinghydrodynamic lift.

2. A seaplane as in claim I, wherein a high thrust power plant means iscarried by said body means.

3. A seaplane as described in claim 1, wherein said hydrodynamic liftingmeans comprises at least one retractable supercavitating hydrofoil.

4. A seaplane as described in claim 1, wherein a high thrust power plantmeans is carried by said tail means.

1. A low drag, high density seaplane having performance characteristicslike that of a high speed land plane of approximately the same size,comprising: a central longitudinal aerodynamically designed hull ofapproximately 25 percent reserve buoyancy and having a high length tobeam ratio of approximately 15:1; a first faired strut means connectedat one end thereof to said hull and extending upwardly from said hull; aflapless monowing centrally supported at the other end of said firstfaired strut means, said monowing being located a maximum of one-fourthof the wing chord above the static waterline of said hull therebycreating a ground effect with respect to the water, said monowing havinga spoiler mounted on the upper surface thereof; tip float meansconnected to the extreme ends of said monowing which provide lateral,hydrodynamic stability, the proximity of said tip float means to saidmonowing prevents excessive loss through wing tip vortices; a secondfaired strut means connected at one end thereof and extending upwardlyfrom said monowing; an aerodynamically configured body means including apersonnel carrying section supported at the other end of said secondfaired strut means; tail means removed from said body means connected tosaid hull at the rear end thereof; and a hydrodynamic lifting meansconnected to said hull for producing hydrodynamIc lift.
 2. A seaplane asin claim 1, wherein a high thrust power plant means is carried by saidbody means.
 3. A seaplane as described in claim 1, wherein saidhydrodynamic lifting means comprises at least one retractablesupercavitating hydrofoil.
 4. A seaplane as described in claim 1,wherein a high thrust power plant means is carried by said tail means.